Scale with processor controlled power switching

ABSTRACT

A computation and control module suitable for use in a variety of postal scales as well as other types of mailroom equipment is disclosed. The module includes a microprocessor and associated circuitry; connectors for connecting ROM, which store firmware for controlling the microprocessor, and PROM, which store postal rate charts; an input/output connector; a serial interface for communications with postage meters; a non-volatile memory for storing parameters specific to particular units; and an auxiliary input/output connector. The auxiliary input/output connector is driven by selected, memory mapped interface circuitry mounted on the PROM card. The module also includes a load cell interface and a power supply. In one embodiment switches, responsive to the microprocessor, are provided for sequentially energizing various connectors and interfaces, so as to reduce power requirements. Systems comprising a plurality of computation and control modules are disclosed. Other systems including battery powered modules mechanically and electrically interconnected by a power distribution bus are also disclosed, as a modular power bus.

BACKGROUND OF THE INVENTION

Postal scale are well known in the art; simple spring scales with scalecharts which map a weight range into one or more postal rates havingexisted for decades. More recently, with the increased availability ofsolid state microprocessors, load cells and low-cost analog-to-digital(A/D) converters it has become feasible to provide electronic, digitalpostal scales with greatly increased capabilities. These increasedcapabilities have not been without price however, and part of this pricehas been an increasing demand placed on scale power supplies ascapabilities were expanded. This problem is further aggravated by anyattempt to increase the commonality of components used in a family ofscales and other mailroom products; as disclosed in the commonlyassigned U.S. patent application entitled, General Purpose ProcessorModule Mailroom Equipment, by Flavio Manduley, filed Dec. 20, 1984, Ser.No. 684,411 since clearly any common power supply must be capable ofmeeting the greatest peak demand in its product family.

Thus, it is an object of the subject invention to provide an electronicscale having reduced peak power demands.

It is another object of the subject invention to provide an electronicpostal scale of modular design which may be expanded to an increasedcapacity without an increase in the size of the power supply provided.

Other objects and advantages will be readily apparent to those skilledin the art from consideration of the detailed description set forthbelow and of the attached drawings.

BRIEF SUMMARY OF THE INVENTION

The above objects are achieved and the disadvantages of the prior artare overcome in accordance with the subject invention by means of ascale comprising; a processing unit for controlling the operation of thescale and for computing appropriate postage values for an item to bemailed according to its weight and the desired postal services asspecified by information entered by an operator; an input fortransmission of the information to the processor; and weighing apparatusfor determining the weight of the item, converting the weight to digitalform, and transmitting the digital weight to the processor. The scalealso includes a power supply for providing power to the processing unit,the input, and the weighing apparatus. The power supply is connected tothe input and the weighing apparatus through processor controlledswitches for selectively connecting and disconnecting the input and theweighing apparatus to the power supply as necessary to determine theweight of an item to be mailed and its appropriate postage value. Theprocessing unit is responsive to a switch, or other such device, thatdetects the presence of an item to be mailed on the pan of the weighingapparatus, to initiate the computation of the appropriate postagevalues.

In another embodiment of the subject invention, the processing unitincludes a processor, a first memory operatively connected to theprocessor for storing a program to control the processor and a secondmemory operatively connected to the processor for storing postal rateinformation. The second memory is connected to the power supply througha further processor controlled switch for selectively connecting anddisconnecting the second memory as necessary to compute the appropriatepostage value.

The subject invention advantageously supplies a scale having a reducedpeak power demand wherein various subsystems of the scale are energizedunder processor control only as need to determine the appropriatepostage value.

Other objects and advantages of the subject invention will be readilyapparent to those skilled in the art from consideration of the detaileddescription set forth below and of the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic block diagram of a computation and controlmodule for use in postal scales and other mailroom equipment.

FIG. 2 shows a schematic block diagram of a mailroom system.

FIG. 3 shows a schematic block diagram of a computation and controlmodule substantially similar to that shown in FIG. 1, which furthershows power switching arrangements used to reduce power requirements.

FIG. 4 shows a schematic block diagram of a modular, battery poweredmailroom system.

FIG. 5 shows a plan view of a power bus module.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a computation and control module for use in postage scalesand other mailroom equipment, such as electronic accounting systems, inaccordance with the subject invention. A large printed circuit board 10,commonly known as a "motherboard" supports the various components andconnectors comprising the subject computation and control module. Anintegrated circuit microprocessor and its associated support circuitryare mounted on motherboard 10 to provide intelligence (i.e.,programmable, general purpose computation and control capabilities) forthe subject module. Such microprocessors are well know to those skilledin the art. Typical of such microprocessors is the well known IntelModel 8085, manufactured by the Intel Corp., Santa Clara, CA.Descriptions of the architectural structure of the 8085 and proceduresfor operationally connecting such microprocessors with various memoryand input/output devices may be found in MCS-80/85 Family User's Manual,published by Intel Corp., 1979. Similar microprocessors and informationare available from other manufacturers and are well known to thoseskilled in the art. Accordingly detailed description of themicroprocessor, its associated circuitry and its interface to othercomponents is unnecessary to an understanding of the subject inventionand will not be discussed further.

Connectors 40, 50, 60 are connected to microprocessor 20 to allow theeasy connection of memory modules to microprocessor 20 (the term"connector" as used herein is meant to include both single connectors orgroups of connectors used together to perform a function. Similarly,paddle boards and other sub modules may comprise single units or groupsof related units.) Connector 40 allows 8K to 24K bytes ofread-only-memory (ROM) mounted on paddleboard 42 to be connected tomicroprocessor 20. This memory is used to store the firmware used tocontrol the postal scale (or other item of postal equipment) comprisingthe subject module. Connector 50 allows 8K to 16K bytes ofprogrammable-read-only-memory (PROM) mounted on paddleboard 52 to beconnected to microprocessor 20. This memory is used to store postal ratecharts and zip-to-zone information, which information is used to convertzip codes to postal zones for computing postage. (PROM's are preferredfor storing postal rate data since such data is subject to fairlyfrequent change. However, those skilled in the art will recognize that,once programmed, PROM's and ROM's are functionally the same. Thus,hereinafter, while recognizing that either PROM's or ROM's may be used,"PROM's" will refer to postal rate and zip-to-zone memory while "ROM's"will refer to firmware memory). Connector 60 allows 8K to 16K ofadditional memory (ROM or PROM) to be connected to microprocessor 20 toprovide an expansion capability for larger systems.

Connector 70 is provided to allow microprocessor 20 to communicate witha keyboard and display (not shown) to provide an operator interface.Connector 70 provides, as outputs, a serial data line, a serial clockline, 3 lines of encoded keyboard strobe signals, and a reset signal forclearing the display, all appropriately buffered; and 6 lines ofkeyboard return and an interrupt line as inputs. A+5 volt line andreturn are provided to supply power to the keyboard and display controllogic. This arrangement allows up to 48 keys to be scanned bymicroprocessor 20 using a ccnventional strobe and return technique. Thekeys used will be defined (i.e., their meanings mapped) by informationstored in PROM's 52 so that definitions of keys may be easily changedand an expanded keyboard may be used with the extended postal ratecharts and zip-to-zone information used in more sophisticated models ofpostal scales. (Alternatively the keyboard may be defined by informationstored in firmware ROM's 42).

In other mailroom equipment, such as electronic accounting systems, amore elaborate and extensive keyboard may be required. Such a keyboardand display would include a keyboard/display controller such as themodel 8279 manufactured by the above identified Intel Corp. To allow forthis expansion of keyboard capability the data line may be madebi-directional to communicate with the keyboard/display controller.

Preferably the display may be a conventional multielement flourescentdisplay. High voltage and filament power may be supplied for the displayeither through connector 70 or locally at the display.

Remote display connector 80 parallels the display connections ofconnector 70; providing a data line, data clock and a +5 volt supply andreturn to allow for the provision of a remote display. The remotedisplay would include its own controller and high voltage and filamentsupplies.

Connector 90 is provided to allow connection of the postal scale to apostage meter through a secure communications link. Since the operationof a postage meter is equivalent to the purchase of postage it iscritical that the transmission of postage information from the postalscale to the meter be error free. A proprietary interface and protocolintended for such error free transmission of postal data to a postagemeter is described in U.S. Pat. No. 4,301,507, for Electronic PostageMeter Having Plural Computing Systems to, Soderberg et al, issued Nov.17, 1981, which is hereby incorporated by reference; and is known by thetrade name Echoplex. Connector 90 provides an Echoplex serial data outline and return, a meter trip line, (which includes special protectivecircuitry to prevent the generation of false meter trip signals duringpower on/off transients) and return and a reset line as outputs. Inputsprovided are an Echoplex serial data-in line, a return, and an interruptline. A+5 volt line and return are provided to provide a remotereference level for signal detection, with return. Preferably the +5volt line is short circuit protected.

Connector 90 also provides a unregulated +5 volt line which may be usedto provide power to a two port interface expansion module mounted on aseparate board. In more sophisticated scales such a board allowscommunication with a postage meter and with devices such as electronicaccounting systems.

It should be noted that the Echoplex circuitry provided in the module ofthe subject embodimient does not include optoisolators but relies on theisolators of the connected postage meter. However the two port expansionboard may preferably include a port with isolators for communicationwith devices such as electronic accounting systems which may not includeisolators.

Connector 100 is provided to allow input/output expansion. A number ofundefined lines are connected from firmware connector 40 to connector100. This allows additional input/output circuitry to be mounted on ROMpaddleboard 42. Thus, for example, a field upgrade of a postal scale toprovide a printer output may be achieved simply by changing paddleboard42; the substitute board would not only include firmware to control theprinter but also input/output circuitry which would provide a printerport at connector 100. (Those skilled in the art will recognize thatsince microprocessors such as the 8085 use "memory mapped I/O"; whereinput/output registers are addressed as memory locations, input/outputcircuitry mounted on paddleboard 42 is directly accessable tomicroprocessor 20).

Non-volatile memory 110 comprises a small amount of memory such aselectrically-erasable-programmable-read-only-memory (E² PROM's). Thismemory is discussed separately from other memory since it is used tostore data which is peculiar to particular scales. It is used to storeinformation such as load cell calibration constants, (e.g., zero,correction factors) configuration parameters (e.g., meter in use,automatic set mode) and customer location zip code (for zip-to-zoneconversion). Preferably this data will be stored with redundancy so thaterrors may be detected and, possibly, corrected. It is also preferredthat the data be electrically alterable so that it may be changed orcorrected through microprocessor 20.

Digital interface and connector 120 is provided to allow transmission ofraw digital data from the load cell transducers, after conversion by theassociated analog-to-digital converter (A/D). Details of the design ofthis interface would depend on the particular load cell and associatedcircuitry chosen for the load cell but would be well within theabilities of those skilled in the art. (Numerous patents including U.S.Pat. Nos. 4,139,892 and 4,350,216 show techniques for interfacing loadcells to microprocessors). Having selected a particular interface designand protocol it would be routine for a person skilled in the art toadapt it to a product family of scales; essentially requiring only theprovision of a sufficient number of data bits to allow the desiredprecision through the whole family of scales.

Preferably the load cell subsystem includes its own control processor.This would allow the load cell raw digital data, commonly known ascounts, to be transmitted with error detection/correction redundancy(check sums, etc.) and two way communications; to check status, requestretransmission in the event of an error, etc. Further incorporation of amicroprocessor into the load cell subsystem would reduce the design ofinterface 130 to a routine processor to processor communicationsproblem.

In use the function of the module of the subject invention would becontrolled by the selection of ROM paddleboard 42, PROM paddleboard 52and the information stored in non-volatile memory 110. For example, ifthe module of the subject invention were intended for use in a lowrange, unsophisticated scale with limited keyboard and displaycapabilities board 42 would be chosen lacking input/output circuitry andwith ROM's programmed with firmware appropriate for the intendedunsophisticated application. Board 62 would be selected with PROM'sdefining a limited selection of postal rates and defining a limitedkeyboard. In a very unsophisticated system zip-to-zone information mightbe entered through the keyboard. In such a system non-volatile memory110 would only include load cell calibration constants and nozip-to-zone conversion tables would be provided.

In a more sophisticated system boards 42 and 52 would be selected toprovide increased capabilities, zip-to-zone conversion, increased postalrate information, automatic meter setting, extended keyboarddefinitions, etc. In such a system non-volatile memory 110 would includecalibration constants, configuration parameters and customer locationzip code.

Programming for postal scales is disclosed in U.S. Pat. No. 4,286,325,to Dlugos, et al, for System And Method For Computing Domestic AndInternational Postage, issued Aug. 25, 1981; and U.S. Pat. No. 4,325,440to Crowley, et al, for Method And System For Computing Special Fees In AParcel Postage Metering System, issued Apr. 20, 1982, which are herebyincorporated by reference. Such programming could readily be translatedinto firmware for a particular microprocessor by a person skilled in theart.

Further the module of the subject invention may also readily be used inmailroom systems such as electronic accounting systems, manifestsystems, mailroom management systems or journal printers. (These systemsare well known for use in mailrooms to record records of postal activityfor later retrieval). For example, if the module of the subjectinvention where intended for use in a journal printer, board 42 would beselected to include journal printer firmware and printer I/O circuitryconnected to expansion connector 100. Such a system might well require afull, general purpose keyboard and display and use the bi-directionalserial communications provided through keyboard and display connector70. Data would be received through serial interface 90; and in order toretain data for later retrieval random-access-memory would be providedon paddleboard 62, either through expansion connector 60 and/or byreplacing PROM's on board 52.

FIG. 2 shows a mailroom system comprising a postal scale 200, aconventional electronic postage meter 300 and an electronic system 400.Postal scale 200 comprises module 10-200 in accordance with the subjectinvention, a load cell subsystem 210 which provides count data for theitem weighed through interface and connector 120-200, a port expander220 connected to Echoplex port 90-200 and a specialized postal scalekeyboard and display connected through connector 70-200. Board 42-200provides firmware which controls module 10-200 in accordance with thedesired capabilities. In addition to firmware for computing appropriatepostage value in accordance with the weight of the item and postalinformation input through keyboard and display unit 230 board 42-200also provides firmware for communications with other systems which maybe connected to scale 200. Such communications firmware is selected bythe processor (not shown) of module 10-200 in accordance withconfiguration parameters stored in non-volatile memory 110-200. In thesystem shown module 10-200 would communicate with a conventional postagemeter 300, which may be a meter such as the Model 6500 metermanufactured by Pitney Bowes Inc., Stamford, Conn. and electronic system400. In addition to transmitting postage values and trip signals tometer 300 module 10-200 also transmits postal information such aspostage value, weight destination, zip code, etc. to electronic system400.

Board 52-200 provides appropriate postal rate information andzip-to-zone information for scale 200, and also provides informationdefining the keys of keyboard display unit 230, which is read by aconventional strobe and return technique through connector 70-200.

System 400 may be any of a number of mailroom systems for logging postaldata; such as, electronic accounting systems, journal printers, mailroommanagement systems, etc. Such systems also provide for later retrievalof the data either by printer, downloading to a disk, computerinterface, or other means.

Such a system is shown in FIG. 4 based on module 10-400, which isstructurally identical to module 10-200. Board 42-400 provides firmwarewhich defines the data logging and system control functions. Suchprogramming would essentially involve no more than simple data basemanagement and routine "housekeeping" functions for the system shown andwould be well within the skill of those skilled in the art. Boards52-400 and/or 62-400 would connect RAM memory to module 60-400. Such RAMstorage may be used for temporary storage of logged postal data. (Designof connectors 50 and/or 60 to accept either ROM or RAM memory would be aroutine task well within the capability of those skilled in the art.)

As described above scale 200 communicates with system 400 throughEchoplex connector 90-200 and expander 220. System 40 also communicatesthrough Echoplex connector 400 and may include expander 420 to allowcommunication with additional scales.

Device 410, which, as indicated above, may be a printer or other meansfor retrieving logged data, is connected to module 10-400 throughconnector 100-400 and appropriate interface circuitry on board 42-400.

Non-volatile memory 110-400 may contain configuration parameters suchthe number of scales connected to system 400, the particular model ofprinter connected, etc.

Because an operator may need to exercise greater control over system 400it includes a general purpose keyboard and display unit 430 whichfurther includes a control unit 432. Control unit 432 communicates withmodule 10-400 through the bi-directional data line of connector 70-400.

Because power supply 30 provides power to all the active components onmotherboard 10 as well as other components attached to motherboard 10 itmust be sized to support the largest system in which it may be used.Accordingly, to avoid burdening less sophisticated systems with the costof an oversized power supply FIG. 3 shows an embodiment of the subjectinvention having a reduced power requirement.

FIG. 3 shows a module which is substantially the same functionally asthe module shown in FIG. 1. (Note that the communications links betweensubsystems are the same but are not shown in FIG. 3 for ease ofillustration). Normally open CMOS switches 55, 65 75, 95, 115 and 125are connected in series with the +5 volt lines of connectors 50, 60, 70,90, non-volatile memory 110 and connector 120, reducing the stand-bypower drain on power supply 30. Switch assembly 25 connects the +5 voltsource to an interrupt input of microprocessor 20 and is actuated,either mechanically, electro-optically, or in some other suitablemanner, by motion of the scale pan (not shown). In response to theinterrupt microprocessor 20 would command power control circuit 130 toclose switch 125 to energize the load cell subsystem (not shown) anddigital load cell interface 120, so that the weight counts from the loadcell subassembly can be generated and transmitted. When a stable countinput is received switch 125 is opened and switch 115 closed so that theparameters stored in non-volatile memory 110 may be retrieved. Switch115 is then opened and switch 75 is closed so that the operator mayenter the necessary information for the item to be mailed. (Note thatpreferably a separate, unswitched +5 volt source 72 is also provided toconnector 80 to keep the keyboard of the keyboard/display unit (notshown) live so that operation of the scale may also be initiated fromthe keyboard). Switch 75 is then opened and switch 50 and, if necessary,switch 60 are closed to energize boards 52 and 62 so that necessarypostal rate information and zip-to-zone conversion information may beretrieved. The appropriate postage value for the item to be mailed isthen determined by microprocessor 20 and switches 55 and 65 are opened.If the configuration parameter information retrieved from non-volatilememory shows a postage meter connected switch 95 is closed to energizethe Echoplex interface and connector 90 for transmission of the postagevalue information to such meter. Switch 75 is then opened andmicroprocessor 20 returns to a wait state until the next interrupt (orcommand from the keyboard).

Thus, the peak power demands on supply 30 are substantially reduced,allowing use of a smaller less costly supply. In less sophisticatedsystems, with low peak power requirements, power controller 130 may beomitted and switches 55, 65, 75, 95, 115 and 125 may be replaced, wherenecessary, with jumpers to reduce the cost of the module and to simplifythe firmware.

In another embodiment of the subject invention the ROM's and PROM's ofboards 42, 52 and 62 may be replaced with battery powered memorymodules. Such modules are disclosed in commonly assigned U.S. patentapplication Ser. No. 590,670, for Postal Rate Memory Module withIntegral Battery Power, by Flavio Manduley, filed Mar. 19, 1984, whichis hereby incorporated by reference. By incorporating battery power onboards 43, 52 and 62 additional memory may be added for moresophisticated systems without need for a larger power supply. Further,incorporating battery power on boards allows preprogrammed RAM's to beshipped to users for postal rate updates, etc. and the use of only RAMmemory with the module of the subject invention simplifies it use inapplication such as journal printers and electronic accounting systemswhere RAM storage is needed.

With the availability of low power CMOS logic and low power displays itis possible to extend the idea of battery powered modules to encompassentire battery powered modular systems. Such a system is shown in FIG.4. A module in accordance with the subject invention 10-500 comprisesbattery powered paddleboards, 42-500 and 52-500, a battery power supply30-500, and incorporates low power CMOS circuitry for active components.A load cell, or other pressure transducer, subsystem 510 utilizing lowpower circuitry 518 for amplifiers and A/D's is connected to module10-500 through connector 120-500 and a low power keyboard and displaysubsystem 530 is connected through connector 70-500. Suitable low powerload cell subsystems are known in the art and include low power modularload cells manufactured by the Toledo Scale Division of RelianceElectric Co., Worthington, Ohio, capacitance transducers manufactured bySerta Corp., Massachusetts, and Digital Mass Transducers manufactured byK-Tron, Arizona Corp., Scottsdale, Ariz. Similarly low power displaysand keyboards are available, ranging up to the typewriter type keyboardand multiline display used in the current generation of "laptop"computers.

Each subsystem includes its own battery power supply 515 and 535; againso that battery 30-500 need not be sized to supply the largest systemcontemplated.

Batteries 30-500, 515 and 535 are interconnected by a low impedanceexternal power bus 550 to reduce noise problems and also to mechanicallyinterconnect the subsystems.

Bus 550 is formed from a plurality of substantially identical segments560, shown in FIG. 5. Segment 560 comprises two substantial, lowimpedance conductors 562 and 564; for +5 volts and ground respectively.Conductors 562, 564 are held in parallel, fixed relationship bysubstantially rigid separator 566. Spaced along conductors 562 and 564are polarized sockets 568a and 568b into which various battery poweredsubsystems may be plugged. The sockets are spaced closely enough thatmultiple connections may be made by each subsystem in order to minimizenoise problems.

The ends 562m, 562f, 564m and 564f are shaped to mate with thecorresponding ends of similar segments 560. At one end of separator 566a captive thumbscrew 570 is mounted and a corresponding tapped bore 572is provided at the other end so that a low impedance mechanically strongbus system may be formed by screwing together a plurality of segments566. Mechanical and power connections between the subsystems of abattery power system such as that shown in FIG. 4 are made by pluggingthe subsystems into the bus so formed.

Returning to FIG. 4 the power drain on batteries 30-500, 515 and 535 maybe further reduced by provision of switches 25,500 and 125-50 tosequentially connect subsystems as required; substantially in the samemanner as described above with respect to the embodiment of FIG. 2.

The embodiments of the subject invention described above and shown inthe attached drawings have been given by way of illustration only. Thoseskilled in the art will recognize numerous other embodiments within thescope of the subject invention.

What is claimed is:
 1. A postal scale comprising:(a) processing meansfor controlling the operation of said scale and for computingappropriate postage values in accordance with the weight of an item tobe mailed and postal information entered by an operator, said processingmeans being controlled by a stored program; (b) input means fortransmission by said operator of said postal information to saidprocessing means; (c) weighing means for determining the weight of saiditem to be mailed, for converting said weight to digital form, and fortransmitting said digitized weight to said processing means; (d) a powersupply for supplying power to said processing means, said input meansand said weighing means; (e) power switching means, responsive to saidprocessing means, for selectively connecting said input means and saidweighing means to said power supply as necessary to determine saidweight and compute said postage values and then disconnecting saidmeans, so as to reduce power requirements; and, (f) sensing means fordetecting the presence of an item to be mailed on said weighing meansand, in response, initiate the determination of the appropriate postagefor said item by said processing means.
 2. A postal scale as describedin claim 1 wherein said processing means further comprises:(a) aprocessor for controlling the operation of said scale and for computingsaid appropriate postage values in accordance with a predeterminedprogram; (b) first memory means connected to said processor for storingsaid program; (c) second memory means connected to said processor forstoring postal rate information; (d) second power switching means,responsive to said processor, for selectively connecting said secondmemory means to said power supply as necessary to compute said postagevalues and then disconnecting said memory means so as to reduce powerrequirements.
 3. A postal scale as described in claim 2 wherein saidpower supply comprises a battery.
 4. A postal scale as described inclaim 3 wherein said processing means, said input means, and saidweighing means each form a modular subsystem.
 5. A postal scale asdescribed in claim 2 wherein said processing means, said input means,and said weighing means each form a modular subsystem.
 6. A postal scaleas described in claim 5 wherein each of said modular subsystems furthercomprises a battery connected to a common power bus.
 7. A postal scaleas described in claim 1 wherein said power supply comprises a battery.8. A postal scale as described in claim 7 wherein said processing means,said input means, and said weighing means each form a modular subsystem.9. A postal scale as described in claim 1 wherein said processing means,said input means, and said weighing means each form a modular subsystem.10. A postal scale as described in claim 9 wherein each of said modularsubsystems further comprises a battery connected to a common power bus.11. A postal scale as described in claim 1 further comprising a generalpurporse module, said module comprising:(a) said processing means (b) apower supply (c) first connector means for connecting signals from saidweighing means to said processing means and for connecting said powersupply to said weighing means; (d) second connector means for connectingsignals from said input means to said processing means and forconnecting said power supply to said input means; and (e) said switchingmeans.
 12. A postal scale as described in claim 11 wherein saidprocessing means further comprises:(a) a processor for controlling theoperation of said scale and for computing said appropriate postagevalues in accordance with a predetermined program; (b) first memorymeans connected to said processor for storing said program; (c) secondmemory means connected to said processor for storing postal rateinformation; (d) second power switching means, responsive to saidprocessor, for selectively connecting said second memory means to saidpower supply for periods necessary to compute said postage value andthen disconnecting said memory means so as to reduce power requirements.13. A postal scale as described in claim 12 wherein said processingmeans, said input means, and said weighing means each form a modularsubsystem.